(i) Technical Field
The present invention relates to an electrostatic image developing toner, an electrostatic image developer, a toner cartridge, a process cartridge, and an image forming apparatus.
(ii) Related Art
As an electrophotography process, various methods are known. In the electrophotography process, a latent image is electrically formed in various ways on a photoreceptor using a photoconductive material. The latent image is developed as a toner image using a toner. The toner image is transferred to an image receiving member, such as paper, optionally through an intermediate transfer member. Next, the toner image is fixed by heating, pressing, heating and pressing, solvent vapor or the like. A fixed image is formed through the plurality of processes. The toner that remains on the photoreceptor is cleaned by various methods. These processes are repeatedly performed.
In recent years, with the technical development in the electrophotography field, the electrophotography process is used for typography, as well as a copy machine and a printer. Then, copies having the same quality and colors as the printed matters are strongly demanded, together with high-speed processing and reliability of the apparatus. It is important for the toner to have high glossiness, high chromaticity, high stress resistance against high-speed processing, and long lifespan. Especially in recent years, energy saving is important. For example, in the electrophotography process, the amount of power consumed during a fixing process needs to be reduced.
As the binder resin, polyester resin is used in view of fixability improvement and storage ability. In recent years, styrene-acrylic copolymer resin is used in view of manufacturability of a polymerized toner. For a high gloss image, polyester resin has suitable melting characteristics.
To synthesize the polyester resin, an organic tin catalyst is widely used.
For the fixing condition, various conditions, such as the environment and the image receiving member to be used, are considered. A high-quality image having high glossiness and chromaticity is demanded even under a condition other than the general fixing condition. For example, when the temperature exceeds 30° C. and ten images or more are successively output using an OHP sheet during the summer, since the environmental temperature is high, the image receiving member (transparency) is insufficiently cooled. Further, since the image receiving member itself has large heat capacity, when successive copying is performed, a subsequently heated recording medium is discharged and stacked on a previously discharged recording medium before the image receiving member is cooled. For this reason, it may take several minutes until the toner image is solidified. In this period, since crystalline resin is crystallized at a relatively slow speed, chromaticity is degraded due to light scattering of the crystal, and image gloss may be degraded by the crystal domain. This phenomenon may occur when a recording medium having large heat capacity of the basis weight of 256 g/m2 or more, such as resin-coated paper or cast-coated paper, is used, and successive output is performed at a slow output speed to improve image gloss (glossiness), as well as when the OHP sheet is used.